The present disclosure relates to dual carrier amplifier circuits and methods.
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Amplifier circuits are basic building blocks of many electronic systems. Amplifier circuits (or “amplifiers”) are used to increase a particular characteristic of a signal, such as voltage, current, or power, for example. One type of amplifier is the transconductance amplifier. In a transconductance amplifier, an input voltage signal is converted into a current output signal. The relationship between the input voltage signal and current output signal is the transconductance (“Gm”) of the amplifier. Transconductance is described by the following equation:Io=Vin*Gm 
One issue with transconductance amplifiers is the variation of amplifier characteristics across different loads. For example, different loads may draw different amounts of current from the output of the transconductance amplifier, thereby changing the characteristics of the amplifier.
Wireless receivers use low noise amplifiers (“LNAs”) to amplify radio frequency (“RF”) signals received from an antenna. In some wireless applications, an RF signal may include multiple channels with multiple carrier frequencies. To process such signals, an LNA may send the amplified RF signal to different signal paths. If a transconductance amplifier were used for the LNA, the different signal paths would alter the loading on the transconductance amplifier output, thereby resulting in signal degradation and a reduced signal-to-noise ratio (“SNR”).
Particular embodiments described below provide improved amplifiers for driving different signal paths. Particular embodiments further provide processing for dual or multi-carrier signals, such as in a wireless receiver.